Acid solutions, and the

Arsenic present only in traces (in any form) can be detected by reducing it to arsine and then applying tests for the latter. In Marsh s test, dilute sulphuric acid is added dropwise through a thistle funnel to some arsenic-free zinc in a flask hydrogen is evolved and led out of the flask by a horizontal delivery tube. The arsenic-containing compound is then added to the zinc-acid solution, and the delivery tube heated in the middle. If arsenic is present, it is reduced to arsine by the zinc-acid reaction, for example ... 

In the preparation of bromo compounds by the Sandmeyer reaction, the amine is generally diazotised in sulphuric acid solution (or in hydrobromic acid solution), and the resulting aryldiazonium sulphate (or bromide) is treated with a solution of cuprous bromide in excess of hydrobromic acid the addition... 

Solid Compounds. The tripositive actinide ions resemble tripositive lanthanide ions in their precipitation reactions (13,14,17,20,22). Tetrapositive actinide ions are similar in this respect to Ce . Thus the duorides and oxalates are insoluble in acid solution, and the nitrates, sulfates, perchlorates, and sulfides are all soluble. The tetrapositive actinide ions form insoluble iodates and various substituted arsenates even in rather strongly acid solution. The MO2 actinide ions can be precipitated as the potassium salt from strong carbonate solutions. In solutions containing a high concentration of sodium and acetate ions, the actinide ions form the insoluble crystalline salt NaM02(02CCH2)3. The hydroxides of all four ionic types are insoluble ... 

Aqueous sulfamic acid solutions are quite stable at room temperature. At higher temperatures, however, acidic solutions and the ammonium salt hydroly2e to sulfates. Rates increase rapidly with temperature elevation, lower pH, and increased concentrations. These hydrolysis reactions are exothermic. Concentrated solutions heated in closed containers or in vessels having adequate venting can generate sufficient internal pressure to cause container mpture. An ammonium sulfamate, 60 wt % aqueous solution exhibits mnaway hydrolysis when heated to 200°C at pH 5 or to 130°C at pH 2. The danger is minimised in a weU-vented container, however, because the 60 wt % solution boils at 107°C (8,10). Hydrolysis reactions are ... 

The only satisfactory method of preparing /3-naphthoquinone is by the oxidation of 1,2-aminonaphthol in acid solution, and the chief problem involved is that of the preparation of this intermediate in suitable yield and purity. This problem and the literature pertaining to it are discussed elsewhere. Most reports of the preparation of the aminonaphthol include some description of its oxidation, but the only particularly helpful comment on the reaction is that ferric chloride is a better oxidizing agent than chromic acid because at a low temperature it docs not attack the quinone, even when present in excess. ... 

It is evident therefore that Fe salts dissolved in water produce highly acidic solutions and the simple, pale-violet, hexaaquo ion only predominates if further acid is added to give pH - 0. At somewhat higher values of pH the solution becomes yellow due to the appearance of the above hydrolysed species and if the pH is raised above 2-3, further condensation occurs, colloidal gels begin to form, and eventually a... 

Alkylquinazolines are catalytically reduced to the corresponding 3,4-dihydro derivatives/ The only example of a 4-substituted quin-azoline which was reduced to its 3,4-dihydro derivative is 2-chloro-4-phenylquinazoline which gave 4-phenyl-3,4-dihydroquinazoline/ 4-Methylquinazolines are susceptible to oxidation, as is shown by the attempted nitration of 2,4-diraethylquinazoline which causes the removal of the methyl group with formation of 4-hydroxy-2-methyl-6-nitroquinazoline/ When the 4-substituent is —C(Et) (C02Et)2 recrystallization of the picrate from ethanol is sufficient to convert it to 4-hydroxyquinazoline/ Similar hydrolyses occur in acid solution and the mechanism undoubtedly involves a hydrated intermediate/... 

The cymidiu sulphouic acid is then diazotised in the usual manner by treating with sodium nitrite in acid solution and the diazo body reduced with alkaline tin chloride solution, or with formic acid and powdered copper, or with other relatively gentle reducing agents. The 3 or 5 cymidin sulphonic acid gives by the above process one and the same cymene sulphonic acid, viz., l-methyl-3-sulphonic-4-isopropyl benzene. 

According to U.S. Patent 3,225,030, 1,500 grams of dried ground plant of Vinca rosea were Intimately mixed with 1,000 ml of a 2% tartaric acid solution, and the mixture was extracted with three 9-liter portions of benzene. The benzene extracts were combined and were concentrated in vacuo to about 1,500 ml. The concentrate was mixed with 1 liter of 2% tartaric acid and the mixture was steam-distilled under reduced pressure until all of the benzene had distilled over. The insoluble residue was dissolved in hot methanol, a second 1-liter portion of 2% tartaric acid solution was added, and the mixture was steam-distilled under reduced pressure until all of the methanol had distilled. 

The extraction of metals by liquid amines has been widely investigated and depends on the formation of anionic complexes of the metals in aqueous solution. Such applications are illustrated by the use of Amberlite LA.l for extraction of zirconium and hafnium from hydrochloric acid solutions, and the use of liquid amines for extraction of uranium from sulphuric acid solutions.42,43... 

M), and inserting a silver-silver chloride electrode. Provided that the internal hydrochloric acid solution is maintained at constant concentration, the potential of the silver-silver chloride electrode inserted into it will be constant, and so too will the potential between the hydrochloric acid solution and the inner surface of the glass bulb. Hence the only potential which can vary is that existing between the outer surface of the glass bulb and the test solution in which it is immersed, and so the overall potential of the electrode is governed by the hydrogen ion concentration of the test solution. 

H- and 3//-Azepines are generally unstable in aqueous acid solution and the few examples of simple azepinium salts, namely perchlorates,77 bromides,105 picrates35201 and a solitary iodide,105 have been prepared under nonaqueous conditions. The fractional crystallization of oxalate salts has been used for the separation of mixtures of 4- and 6-substituted 3f/-azepines,66 and 3,6-di-tm-butyl- and 2,5-di-tert-butyl-3//-azepine, on treatment with tetrafluoroboric acid in acetonitrile, are converted quantitatively into their crystalline tetrafluoroboratc salts.70... 

Nitrous acid can have both a catalytic and an anticatalytic effect on aromatic nitration, the former being appropriate in dilute (ca. 6 M) nitric acid solutions and the latter appropriate to more concentrated solutions. 

According to this mechanism, it is the free amine, not the salt that reacts, even in acid solution and the active-hydrogen compound (in the acid-catalyzed process) reacts as the enol when that is possible. This latter step is similar to what happens in 12-4. There is kinetic evidence for the intermediacy of the iminium ion (13). 

When the oxide is formed by anodizing in acid solutions and the sample is then left to rest at the OCP, some dissolution can occur. This process has been studied by a numbers of authors,70-75 especially in relation to porous oxides [cf. Section 111(4)]. It was found that pore walls are attacked, so that they are widened and tapered to a trumpet-like shape.70 71 Finally, the pore skeleton collapses and dissolves, at the outer oxide region. The outer regions of the oxide body dissolve at higher rates than the inner ones.9,19 The same is true for dissolution of other anodic oxides of valve metals.76 This thickness dependence is interpreted in terms of a depth-dependent vacancy concentration in the oxide75 or by acid permeation through cell walls by intercrystalline diffusion, disaggregating the microcrystallites of y-alumina.4... 

Recall for dilution, Mx Vx = M2V2. In this instance, the acetic acid solution and the calcium acetate solution are diluting each other. 

Erifon A process for making cellulose textiles flame-resistant. Titanium and antimony oxychlorides are applied from acid solution and the cloth is then neutralized with sodium carbonate solution. Invented by Du Pont in 1947. See also Titanox FR. 

The author has found the following GLC procedure to be suitable to determine the purity of sodium valproate and valproic acid. Preparatory to chromatography, the sodium valproate was acidified with a strong aqueous hydrochloric acid solution, and the valproic acid which is practically insoluble in water was separated. The separated free acid was then analyzed. 

The most stable oxidation states of chromium in the subsurface environment are Cr(III) and Cr(VI), the latter being more toxic and more mobile. The oxidation of Cr(III) in subsurface aqueous solutions is possible in a medium characterized by the presence of Mn(IV) oxides. Eary and Rai (1987), however, state that the extent of Cr(III) oxidation may be limited by the adsorption of anionic Cr(VI) in acidic solutions and the adsorption and precipitation of various forms of Cr(OH). These authors also report a rapid quantitative stoichiometric reduction of aqueous Cr(VI) by aqueous Fe(ll), in a pH range covering the acidity variability in the subsurface even in oxygenated solutions. 

Finally, 5 ml of the polyfvinyl alcohol) solution are mixed with 5 ml of periodic acid solution and the flow time is determined immediately and then at short time intervals until a constant value is reached after a few minutes. 

Perchloric acid is the strongest of the common acids in acetic acid solution and the titration medium usually used for non-aqueous titration of bases is perchloric acid in acetic acid. Addition of acetic anhydride, which hydrolyses to acetic acid, is used to remove water from aqueous perchloric acid. Weak bases compete very effectively with acetic acid for protons. Oracet blue, quinalidine red and crystal violet (very weak bases) are used as indicators in this type of titration. A typical analysis is shown in Figure 3.8 for LDOPA. 

It is pertinent to record that the differences in the properties of compounds of selenium and tellurium in hydrochloric acid solution and the formation of several types of complex ion by these elements are the basis of extraction and ion-exchange methods of separating selenium and tellurium.1... 

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